Apparatus for conditioning metai surfaces for spray metal bonding



1943. A. P. SHEPARD APPARATUS FOR CONDITIONING METAL SURFACES FOR SPRAYMETAL BONDING Filed Nov. 25, 1940 2 Sheets-Sheet 1 INVENTOR.

A.P.'SHEPIA\RD A ,335,

APPARATUS FOR CONDITIONING METAL SURFACES FOR SPRAY METAL BONDING File dNov. 25, 1940 2 Sheets-Sheet 2 lHllllEilHlllliiiiiii INVENTOR BY IAmuEZwz a ATTOM Patented Nov. 30, 1943 iTED STTES APPARATUS FOR commonmotm'rsr SURFACES FOR SPRAY METAL BONDING Arthur P. Shepard, Forest Hills,uen Island,

N. Y... assignor parry,

tron oi New Jersey to Metallizing Engineering Com- Inc., Long IslandCity, N. EL, a. corpora- Application November 25, 1940, Serial No.366,957 2 Claims. (ciao-5.1)

This is a continuation in part of my application Serial No. 221,650,filed July 27, 1938. l

The invention relates to a new and useful apparatus for conditioningmetal surfaces for spray metal bonding, and will be understood from thefollowing description read in conjunc-.

tion with the drawings in which-- Fig. 1 is an enlarged cross-sectionthrough a metal block having a pitted surface;

Fig. 2 an enlarged section through a metal block having a grit blastedsurface;

Fig. 3 is a cross-section through one embodi ment of the invention;

Fig. i is a side view of part of the construction shown in Fig. 3;

Fig. 5 is an enlarged edge view of part of the construction shown inFig. 4;

Fig. 6 illustrates an enlarged cross-section through a metal blockhaving a surface prepared with a tool having teeth of an apex angle inexcess of 120 Fig. '7 is an enlarged cross-section through a metal blockshowing a surface prepared with a tool having large and widelyspacedteeth;

Fig. 8 is an enlarged cross-section through a metal block showing asurface obtained by the application of the tool in accordance with theinvention. I

The application of metal coatings to metal surfaces by metal spraying isachieved by the use of a metal gun, i. e., a device by which metal isfed to a heating zone from which zone metal particles, at least some ofwhich are molten or in a heat plastic condition, are propelled againstthe object or surface by a blast of air or other gas. In order to obtaina coating on the object or surface sprayed, it is essential that themetal particles as they impinge upon the surface sprayed enter into asatisfactory bond with suchbetween spray metal and a metal base; it isrequisite that the surface to be sprayed have a certain type and degreeof roughness, principally characterized by two requirements. The firstis that the surface not only be very rough-but that it have a particularkind of roughness, i. e., a roughness in which the depressions areoverhung by projections of metal so as to provide undercut cavities.These cavities act as minute dovetailed keyways and interlock with thesprayedmetal particles to form a strong bond. If the overhanging metalprojections and dove-talled cavities are absent, the bond between thespray metal and the base will not be satisfactory, no matter how roughor pitted a surface may otherwise be as, for example, a surface ofthetyp obtained by knurling or the like, illustrated by numeral 50 inFig. 1. The second essential requirement for the surface roughness isthat the-indentations and metalprojections be of a particularsize andspacing. Since the size of the sprayed metal particles is very fine, thedepressions and projections of the roughened surface must also besumciently fine to form a proper. interlocking structure. .On the otherhand, the roughness represented by the ,de-' ,pressions and projectionsmust not be too fine,

as otherwise the metal particles could not penetarte into thedepressions and hence no satisfactory bond could be secured.

A surface of the desired type roughness meeting both of the primaryrequirements for satisfactory spray metal bonding, is conventionallyobtained by sand or grit blasting, using as the recommended material a#30 to #40 sharp, ans gular 'steel grit which, when blown throughaproper nozzle with an air pressure of approximately to pounds per squareinch, will produce a very rough and irregular surface on the metal basebeing blasted, having a multiple number of closely spaced dove-tailedcavities. Such sand or grit blasted surface is, for instance, illusetrated by numeral 50 in' Fig. 2 which shows an; enlarged section througha metal block, the surface of which was grit blasted in this manner. Thetool in accordance with my invention is designed. to simulate as closelyas possible the type of rougened surface which is producedby grit orsand blasting and which meets the essential requirements forsatisfactory spray metal bonding to a metal base. The tool thuseliminates the costly operation of blasting; it replaces the expensivegrit blasting equipment and permits the roughening operation, ifdesired, in the same machine tool in which extra machine set-ups.

The instrument which I have invented and which may be utilized to treata metal surface in simulation of sand or grit blasting so as tostrongmachining and spraying i is to be carried out, thereby obviatingone or more 1y bond thereto applied spray metal may be convenientlydescribed in connection with the preferred embodiment of my inventionillustrated'in Figs, 3, 4 and 5. As there shown, a group I of steeldiscs is carried by spool 2 and held by nut 3 and lock-nut 4 in contactwith the spool and with one another. Spool 2 and disc assembly I arecarried by shaft 5. Spool 2 is secured between shoulder 6 integral withshaft and machine screw 1. By removing screw 1, spool 2 and discassembly I may be removed from the shaft when desiredand replaced by anew spool and disc assembly. Shaft 5 is rotatably carried inball-bearings Ill and II mounted in block I provided with extension l3.This extensionis of such size and proportions that it may be insertedand secured in the ordinary lathe tool post or similarly mounted in thetool holder of a machine tool such as a planer, shaper or boring mill.In an alternative embodiment of this phase of my asaasie invention,spool 2 and disc assembly I may be ,similarly carried on a shaftprojecting beyond the spool on either side and each end of this shaftmay be mounted in a bearing, which bearing is carried by one tyne of atwo-tyned fork forming atool which may similarly be manipulated by handor secured in .a machine tool post. The construction shown in Fig. 3 hashowever, the advantage that if used 'on work which has a projectingshoulder the disc assembly may be worked closer to the shoulder than thealternative type in which the disc assembly is carried between the tynesof a forked handle.

Each of the discs 8 (Fig. 4) is provided with teeth 9. The teeth of theassembled discs are not in alignment but are staggered with respect toone another. This is illustrated in Fig, 5 in which l5 designates thevertices of the teeth and IS the valleys between the teeth of alternatediscs, while I! designates the vertices and I8 the valleys between theteeth of the other discs. The arrangement of the plurality of rows ofsharp teeth, in such, manner that some of the teeth of some rows are outof line with some of the teeth of other rows is essential for otherwisethe teeth will tend to continue to relocate in the depressions firstmadeand form a surface of the type illustrated in connection with Fig. 1having no dove-tailed cavities and being not a satisfactory spray metalbonding surface.

The apex angle ofthe teeth is critical for the successful operation ofthe device as I have found it necessary for the purpose of obtaining theproper type of surface roughness to get a reason-v ably narrow hole andthen by afurther action of the tool to split or peen the projectionadjacent the hole so that the same will overhang the hole. When the apexangle of the teeth is too great,

, i. e., in excess of approximately 120, such re sult cannot be achievedto a satisfactory degree for the hole produced by such. teeth is toowide in relation to its depth to permit the edges to become properlypeened o'ver'the hole by the subsequent action of the tool. This is forinstance illustrated in" Fig. 6 which represents a typeof surface (52)produced by a tool with an. apex angle greater than 120 and which showsthe surface, though out and roughened, yet to have insuflicientoverhanging projections to secure the proper bond between the spraymetal and the metal base. On the other hand, if the apex angle oftheteeth is less than approximately 45? tool steel. In most cases,however, I prefer, for best results, an apex angleof the teeth ofapproximately 90.

The size and spacing of the teeth on each of the rows of teeth of thetool in accordance with the invention is also critical for theproduction of a satisfactory spray metal bonding surface. I havediscovered it essential to provide for a pitch of rows of teeth of notin excess of approximately $4 and a pitch of the teeth in the directionof the circumference of each row of teeth not less thanapproximately normore than approximately 4 teeth per linear inch. If the teeth do notmeet these dimensional and spacing requirements and are for instance toolarge and spaced too far apart, and are consequently forced too deeplyinto the base to which the tool is applied, an unsatisfactory type ofsurface results, which surface'is, for instance, typified by the solidsurface lines 53 in Fig. I. If the metal of the base .iections (54) willbreak on when drawn or worked through too great a distance by therepeated action of the tool, leaving the surface as indicated by thesolid surface line without any appreciable amount of satisfactory,overhanging projections essential to'the anchoring of the spray metalwhen applied to such surface. Furthermore, a tool having teeth that aretoo large and too widely spaced would be substantially incapable ofproducing such close spacing of the individual cavities essential forthe conditioning of a metal surface for spray metal bonding as isrepresented by the relatively fine texture of a, sand or grit blastedsurface.

I have found it necessary to so construct the tool that the individualteeth will strike the metal with as near as possible perpendicularmotion to the surface being prepared. This gives a chopping and peeningeffect which first cuts holes and then flays and peens the projectionsso that some of the metal of the projections overhangs the relativemotion tangential to the surface being prepared, the teeth will cut'outa smooth hole and after the first series of holes is produced,

' subsequent action of the teeth'when'having any the teeth will breakand become dull under the severe action to which they are subjectedwhich is true even if the teeth are made of hardened frictional drag,will cut off the very delicate projections of metal rather thansplitting and peening them as is required.

In the practical application of the tool in accordance with myinvention, the base to be sprayed is worked with the tool by moving thesame back and forth over the surface will the de sired roughness isobtained. The thus roughenedsurface does not present a succession ofholes corresponding to the form of the disc teeth since the teeth do nottrack or mesh in the surface of the work but on the contrary, come downat random and in such a way, as above-pointed out, that the surfacebetween the teeth marks first formed is splayed and peened by subsequentimpacts with the teeth to form minute cavities with overhanging outeredges. The base'to be sprayed upon is preferably secured in anappropriate metal working machine, as, forinstance,

a lathe or planer while the tool is preferably secured in the toolholder of the machine and acts upon the surface of the base to betreated passing over and in contact with the same. The surface obtainedon a metal base by the application of the tool in accordance with theinvention is, for

v instance, illustrated in Fig. 8. The surface (ll) there shown closelyresembles that of a sand or Irlt blasted surface.

The foregoing description is furnished by way of illustration and not oflimitation and it is, therefore, my intention that the invention belimited only by the appended claims or their equivalents wherein I haveattempted to claim broadly all inherent novelty.

I claim:

1. A tool for'producing a simulated sand blasted 1 surface on metal forspray metal bonding, com-v prising a piece adapted to be held in amachine tool holder, a shaft mounted in said piece and a wheel carriedby said shaft comprising a plu rality of circumferential rows of metalpeening and splaying teeth, at least the majority of said teeth eachdefining an apex angle of not inex cess of approximately 120 and noticesthan anproximately 45, 881d wheel being freely rotatable said rows ofteeth having a circumferential pitch 10 of not less than approximately30 nor more than approximatley 4 teeth per linear inch.

2. A tool for producing a simulated sand blasted surface on metal forspray metal bonding comprising a piece adapted to be held in a machinetool holder, a shaft mounted in said piece and a plurality of toothedmetal discs carried by said shaft and freely rotatable about the axis ofsaid shaft, at least the majority of said teeth being metal splaying andpeening teeth and each de- 20 fining an apex angle. of approximately 90,the

peening and splaying surfaces ofthe teeth of at least some of said discsbeing out of line with respect to the peening and splaying surfaces ofthe teeth of other discs, at least the majority of 5 adjacent tootheddiscs having a side spacing substantially parallel to said axis of notin excss of aproximately V4" and the teeth of at least the majority ofsaid toothed discs having a circumferential pitch of approximately 18teeth per AR'I'HURRBHEPARD.

30 linear inch.

